Computer graphics systems and methods for synthesizing photorealistic images, i.e., images that cannot be distinguished from photographs, have a wide field of applications, among them being the animated movie industry and product visualization. Photorealistic image synthesis typically requires the simulation of global illumination, which can typically only be approximated in a consistent manner by using ray tracing.
Contrary to rasterization, ray tracing allows one to follow arbitrary transport paths of light. Algorithms that perform physically correct simulations of light transport tend to shoot rays as wide-spread as possible in order to increase efficiency. As a result, most rays that account for global illumination effects are incoherent.
Among examples of prior art approaches, the following are various documents, each of which is incorporated herein as if set forth herein in its entirety:    Benthin, C, “Realtime Ray Tracing on Current CPU Architectures,” Ph.D. Thesis, Saarland University (2006).    Christensen, P., “Ray Tracing for the Movie Cars,” Proc. 2006 IEEE/EG Symposium on Interactive Ray Tracing, pp. 1-6 (2006).    Emst, M, and Greiner, G., “Early Split Clipping for Bounding Volume Hierarchies,” Proc. 2007 IEEE/EG Symposium on Interactive Ray Tracing, pp. 73-78 (2007).    Geimer, M, “interaktives Ray Tracing,” Ph.D. Thesis, Koblenz-Landau University, Germany (2006).    Glassner, A., “An Introduction to Ray Tracing,” Academic Press (1989).    Reshetov, A., “Faster Ray Packets—Triangle Intersection through Vertex Culling,” Proc. 2007 IEEE/EG Symposium on Interactive Ray-Tracing, pp. 105-112 (2007).    Reshetov, A., Soupikov, A., and Hurley. J., “Multi-Level Ray Tracing Algorithm” ACM Transactions on Graphics, Proc. SIGGRAPH 2005, 24(3): 1176-1185 (2005).    Shirley, P, “Realistic Ray Tracing,” A K Peters, Ltd. (2000).    Veach, E., “Robust Monte Carlo Methods for Light Transport Simulation,” Ph.D. Thesis, Stanford University (1997).    Waechter, C. and Keller, A., “Instant Ray Tracing: The Bounding Interval Hierarchy,” Rendering Techniques 2006 (Akcnine-Moller, T., and Heidrich, W., Editors), Proc. 17th Eurographics Symposium on Rendering, pp. 139-149 (2006).    Waechter, C, and Keller, A., “Terminating Spatial Partition Hierarchies by A Priori Bounding Memory,” Proc. 2007 IEEE/EG Symposium on Interactive Ray Tracing, pp. 41-46 (2007).    Wald, I., “On Fast Construction of SAH-Based Bounding Volume Hierarchies,” Proceedings of the 2007 Eurographics/IEEE Symposium on Interactive Ray Tracing (2007).    Wald, I., “Realtime Ray Tracing and Interactive Global Illumination,” Ph.D. Thesis, Saarland University (2004).    Wald, I.; Benthin, C; Wagner, M.; and Slusallek, P., “Interactive Rendering with Coherent Ray Tracing,” EUROGRAPHICS 2001, 20(3): 153-164 (2001).    Wald, I; Boulos, S.; and Shirley, P., “Ray Tracing Deformablc Scenes Using Dynamic Bounding Volume Hierarchies. ACM Transactions on Graphics,”26(1) (2006).    Wald, I.; Mark, W. R.; Gunther, J.; Boulos, S.; Ize, T.; Hunt, W.; Parker, S C.; and Shirley, P., “State of the Art in Ray Tracing Animated Scenes,” Eurographics 2007 State of the Art Reports (2007).
Ray tracing, such as ray tracing as described in a number of the above-listed documents, has a long history, but became interactive only recently. Rapid algorithms to construct the acceleration data structures cut down the preprocessing time and the actual ray tracing speed has been improved by tracing coherent packets of rays using SIMD (Single Instruction Stream. Multiple Data Stream) instructions of current processors. Most of the rays in global illumination computations are incoherent by intention and major parts of the simulation cannot benefit from tracing packets of rays.
However, in order to benefit from SIMD instructions, such SIMD instructions are typically used in a conventional manner by using multiple objects simultaneously, e.g., 4 triangles at a time, 4 bounding boxes at a time, and several split planes at a time. Compared to tracing packets, this has the major disadvantage that memory bandwidth is not reduced.
It would be desirable and valuable to provide computer graphics methods, systems, and computer program products utilizing SIMD instructions in which memory bandwidth requirements can be reduced, and which afford improved performance.